Expand QColorTransform

Add comparison operators and an isIdentity() method to detect (1-1)
transforms.

[ChangeLog][QtGui] Added QColorTransform::isIdentity() method. Added QImage::colorTransformed() transitive method.

Change-Id: I5fbcd14e75f2179e43e94e8c5f42cd0a5600790b
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

3 files changed, 47 insertions, 8 deletions

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 5027a09a09..57900d4379 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -1,4 +1,4 @@
-// Copyright (C) 2021 The Qt Company Ltd.
+// Copyright (C) 2022 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qimage.h"
@@ -4979,6 +4979,8 @@ QImage QImage::convertedToColorSpace(const QColorSpace &colorSpace) const
 {
     if (!d || !d->colorSpace.isValid() || !colorSpace.isValid())
         return QImage();
+    if (d->colorSpace == colorSpace)
+        return *this;
     QImage image = copy();
     image.convertToColorSpace(colorSpace);
     return image;
@@ -5003,6 +5005,8 @@ QColorSpace QImage::colorSpace() const
 */
 void QImage::applyColorTransform(const QColorTransform &transform)
 {
+    if (transform.isIdentity())
+        return;
     detach();
     if (!d)
         return;
@@ -5054,21 +5058,21 @@ void QImage::applyColorTransform(const QColorTransform &transform)
         transformSegment = [&](int yStart, int yEnd) {
             for (int y = yStart; y < yEnd; ++y) {
                 QRgbaFloat32 *scanline = reinterpret_cast<QRgbaFloat32 *>(d->data + y * d->bytes_per_line);
-                transform.d->apply(scanline, scanline, width(), flags);
+                QColorTransformPrivate::get(transform)->apply(scanline, scanline, width(), flags);
             }
         };
     } else  if (depth() > 32) {
         transformSegment = [&](int yStart, int yEnd) {
             for (int y = yStart; y < yEnd; ++y) {
                 QRgba64 *scanline = reinterpret_cast<QRgba64 *>(d->data + y * d->bytes_per_line);
-                transform.d->apply(scanline, scanline, width(), flags);
+                QColorTransformPrivate::get(transform)->apply(scanline, scanline, width(), flags);
             }
         };
     } else {
         transformSegment = [&](int yStart, int yEnd) {
             for (int y = yStart; y < yEnd; ++y) {
                 QRgb *scanline = reinterpret_cast<QRgb *>(d->data + y * d->bytes_per_line);
-                transform.d->apply(scanline, scanline, width(), flags);
+                QColorTransformPrivate::get(transform)->apply(scanline, scanline, width(), flags);
             }
         };
     }
@@ -5097,6 +5101,39 @@ void QImage::applyColorTransform(const QColorTransform &transform)
         *this = std::move(*this).convertToFormat(oldFormat);
 }
 
+/*!
+    \since 6.4
+
+    Returns the image color transformed using \a transform on all pixels in the image.
+
+    \sa applyColorTransform()
+*/
+QImage QImage::colorTransformed(const QColorTransform &transform) const &
+{
+    if (!d || !d->colorSpace.isValid())
+        return QImage();
+    if (transform.isIdentity())
+        return *this;
+    QImage image = copy();
+    image.applyColorTransform(transform);
+    return image;
+}
+
+/*!
+    \since 6.4
+    \overload
+
+    Returns the image color transformed using \a transform on all pixels in the image.
+
+    \sa applyColorTransform()
+*/
+QImage QImage::colorTransformed(const QColorTransform &transform) &&
+{
+    if (!d || !d->colorSpace.isValid())
+        return QImage();
+    applyColorTransform(transform);
+    return std::move(*this);
+}
 
 bool QImageData::convertInPlace(QImage::Format newFormat, Qt::ImageConversionFlags flags)
 {
diff --git a/src/gui/image/qimage.h b/src/gui/image/qimage.h
index fd42813115..9e4abd006e 100644
--- a/src/gui/image/qimage.h
+++ b/src/gui/image/qimage.h
@@ -234,6 +234,8 @@ public:
     void convertToColorSpace(const QColorSpace &);
     void setColorSpace(const QColorSpace &);
 
+    QImage colorTransformed(const QColorTransform &transform) const &;
+    QImage colorTransformed(const QColorTransform &transform) &&;
     void applyColorTransform(const QColorTransform &transform);
 
     bool load(QIODevice *device, const char *format);
diff --git a/src/gui/image/qimage_conversions.cpp b/src/gui/image/qimage_conversions.cpp
index 433134ff7e..fa75bed3c8 100644
--- a/src/gui/image/qimage_conversions.cpp
+++ b/src/gui/image/qimage_conversions.cpp
@@ -1418,7 +1418,7 @@ static void convert_ARGB_to_gray8(QImageData *dest, const QImageData *src, Qt::I
 
     QColorSpace fromCS = src->colorSpace.isValid() ? src->colorSpace : QColorSpace::SRgb;
     QColorTransform tf = QColorSpacePrivate::get(fromCS)->transformationToXYZ();
-    QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
+    const QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
     QColorTransformPrivate::TransformFlags flags = Premultiplied
             ? QColorTransformPrivate::InputPremultiplied
             : QColorTransformPrivate::Unpremultiplied;
@@ -1448,7 +1448,7 @@ static void convert_ARGB_to_gray16(QImageData *dest, const QImageData *src, Qt::
 
     QColorSpace fromCS = src->colorSpace.isValid() ? src->colorSpace : QColorSpace::SRgb;
     QColorTransform tf = QColorSpacePrivate::get(fromCS)->transformationToXYZ();
-    QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
+    const QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
     QColorTransformPrivate::TransformFlags flags = Premultiplied
             ? QColorTransformPrivate::InputPremultiplied
             : QColorTransformPrivate::Unpremultiplied;
@@ -1487,7 +1487,7 @@ static void convert_RGBA64_to_gray8(QImageData *dest, const QImageData *src, Qt:
 
     QColorSpace fromCS = src->colorSpace.isValid() ? src->colorSpace : QColorSpace::SRgb;
     QColorTransform tf = QColorSpacePrivate::get(fromCS)->transformationToXYZ();
-    QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
+    const QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
     QColorTransformPrivate::TransformFlags flags = Premultiplied
             ? QColorTransformPrivate::InputPremultiplied
             : QColorTransformPrivate::Unpremultiplied;
@@ -1526,7 +1526,7 @@ static void convert_RGBA64_to_gray16(QImageData *dest, const QImageData *src, Qt
 
     QColorSpace fromCS = src->colorSpace.isValid() ? src->colorSpace : QColorSpace::SRgb;
     QColorTransform tf = QColorSpacePrivate::get(fromCS)->transformationToXYZ();
-    QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
+    const QColorTransformPrivate *tfd = QColorTransformPrivate::get(tf);
     QColorTransformPrivate::TransformFlags flags = Premultiplied
             ? QColorTransformPrivate::InputPremultiplied
             : QColorTransformPrivate::Unpremultiplied;